Bridge Mode or Access Point? What's the difference? Cascade??

A wireless access point is a device that extends a wired network, into the wireless space - it will have an Ethernet port to connect to the wired network, and radio transceivers to connect to wireless devices. A wireless bridge is an arrangement of devices (minimum two) that link two wired network segments, wirelessly. The bridge concept can be a little difficult to visualize, so let me do a comparison. Let's say you have a road network, carrying vehicular traffic and that road network ends on one side of a river. Now imagine a second road network, on the other side of the river. If you wanted to join those networks, one way to do it would be to build a bridge. A wireless bridge is similar in concept - you would take two wireless access points, connect one to the first wired network, and the other to the second wired network, and then you would put both access points into bridged mode, and tell them only to talk to one another - in bridged mode, the access point would not normally accept connections from client devices. Cascading routers, also known as daisy chaining, is when you connect the WAN side of one router to the LAN side of the other, so you would have internet into the WAN port of one router, and then the WAN port of the second router connected to one of the first router's LAN ports. My suggestion is that you avoid cascading routers wherever possible - it's not that it can't be done, but you'll generally find that it causes more grief than it is worth. I'm inclined to say you have the R7000 misconfigured in some fashion - I can't see it limiting you to a 20 mbps connection when configured as an AP - but - I have no personal experience with them so ...